Review: A buffer solution is prepared by adding 0.125 moles of ammonium chloride to 500. mL of 0.500 M ammonia solution. (Ka of NH4+ is 5.6x10-10) a. What is the pH of the buffer? b. In what ratio should the compounds be added to achieve a pH 10.00? c. If several drops of HCl were added to the original buffer solution, what reaction would take place?

HCl introduces H3O+ and Cl- into the buffer, what will H3O+ react with?

Titrations: 1. A very controlled acid-base reaction

Titrations: 1. A very controlled acid-base reaction 2. Typically, base is added to an acid until ALL INITIAL MOLES OF THE ACID HAVE REACTED AWAY COMPLETELY (only products remain)

Titrations: 1. A very controlled acid-base reaction 2. Typically, base is added to an acid until ALL INITIAL MOLES OF THE ACID HAVE REACTED AWAY COMPLETELY (only products remain) 3. The equivalence point is the point when all moles base added = moles of acid

Titrations: 1. A very controlled acid-base reaction 2. Typically, base is added to an acid until ALL INITIAL MOLES OF THE ACID HAVE REACTED AWAY COMPLETELY (only products remain) 3. The equivalence point is the point when all moles base added = moles of acid 4. The indicator is the “alarm” for when the equivalence points has been reached

5. Titration curves give more accurate data about when the equivalence point has been reached

Strong acid – strong base titrations: Initial pH: Only acid is present, no base yet!

Strong acid – strong base titrations: pH while adding base: Write a rxn, do stoichiometry, find the LR

Strong acid – strong base titrations: Equivalence point: Point at which all moles of acid have reacted with all moles of base

Strong acid – strong base titrations: pH if “over-titrated”: Write a rxn, do stoichiometry, find the LR

Try 1 and 2 on the back now.

Try 1 and 2 on the back now.

Try 1 and 2 on the back now.

Acids and Bases